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Environmental advocacy group Heal the Bay has released a report based on 12 years of data showing concerning conditions in the 110-square-mile Malibu Creek watershed. Angie Crouch reports for NBC4 News on March 19, 2013. (Published Tuesday, March 19, 2013)

A dozen years of data collected by staff and volunteers for Heal the Bay have painted a picture of Malibu Creek and it isn't pretty, they say.

The Santa Monica environmental nonprofit group recently issued a report describing the 110-square-mile watershed as an "ecosystem on the brink."

Those recommendations come after Heal the Bay has spent some 12 years studying the watershed's fragile, diverse environment.

“We acknowledge that people live here and we can’t get rid of development, but that we can actually improve it," said watershed scientist Katherine Pease with Heal the Bay, one of the report's authors.

The 143-page report details conditions in the second-largest watershed that drains into Santa Monica Bay, which curves along the Los Angeles-area coast from Malibu to the Palos Verdes Peninsula. Malibu Creek feeds into world-famous, popular and often polluted Surfrider Beach.

The area has been the subject of significant conservation efforts from authorities at all levels of government – and from researchers and nonprofits such as Heal the Bay. Still, the group argues, it's not enough.

Heal the Bay's "Stream Team" of nearly 6,000 volunteers began collecting water samples and other data in 1998 to assess the health of the watershed, which includes diverse habitat ranging from rare native grassland within the Santa Monica Mountains to coastal sage scrub. Data in the report comes from the years 1998 to 2010.

The watershed includes suburbs – Calabasas, Westlake Village, Oak Park, Agoura Hills and others – that are at higher elevations. Those developed areas send urban runoff into the watershed, contributing to the creek's poor water quality, the report states.

The creek and the streams that flow into it have high fecal indicator bacteria concentrations, the report found. And the waterways are also polluted by trash, runoff, sedimentation and algae, the authors state.

The report describes another problem as "hardened streambanks" that have been stabilized with concrete that causes even more erosion downstream.

"People are worried the stream is washing way, so they put in hard structures to keep it in place," Pease said. "However, that promotes additional erosion ... We get these really eroded stream banks and there’s a loss of habitat."

Rindge Dam, on the lower stretch of Malibu Creek, creates an impassable barrier that does not allow fish through. The report says it should be removed.

Then there are the invasive species that have taken over, sometimes killing native plants and animals. More than a quarter of steam banks in the watershed are lined in invasive vegetation such as fennel. Bullfrogs, crayfish and the New Zealand mudsnail are other invaders causing problems.

Despite all those concerns, the report emphasizes that more than 75 percent of the watershed is comprised by undeveloped areas such as Malibu Creek State Park. The authors argue that mostly natural state provides an "unprecedented opportunity to protect and improve remaining natural resources."